Process for the production of high shrinkage threads yarns and fibersfrom acrylonitrile polymers

ABSTRACT

THIS INVENTION RELATES TO A PROCESS FOR THE PRODUCTION OF HIGH SHRINKAGE THREADS, YARN AND FIBERS FROM ACRYLONITRILE POLYMERS OF COPOLYMERS CONTAINING AT LEAST 50% BY WEIGHT OF POLYMERIZED ACRYLONITRILE AND MIXTURES THEREOF, WHEREIN THE THREAD OR YARN PRODUCED BY THE DRY SPINNING PROCESS IS EXPOSED TO ELEVATED TEMPERATURES IN THE PRESENCE OF STREAM AND IS THEN STRECHED AND DRIED. THE SPUN THREAD OR YARN OBTAINED BY THE DRY SPINNING PROCESS MAY BE CONTECTED WITH SATURATED STREAM UNDER PRESSURE.

United States Patent US. Cl. 269-20 5 Claims ABSTRACT OF THE DISCLOSUREThis invention relates to a process for the production of high shrinkagethreads, yarn and fibers from acrylonitrile polymers or copolymerscontaining at least 50% by weight of polymerised acrylonitrile andmixtures thereof, wherein the thread or yarn produced by the dryspinning process is exposed to elevated temperatures in the presence ofsteam and is then stretched and dried. The spun thread or yarn obtainedby the dry spinning process may be contacted with saturated steam underpressure.

This is a continuation of SN. 755,797, filed Aug. 28, 1968 and nowabandoned.

The invention relates to a process for the production of high shrinkagethreads, yarn and fibers from acrylonitrile polymers or copolymers andmixtures thereof by heat treatment of the polymeric material producedwhich has been dry spun.

Shrinkable fibers are of special interest for the production of highbulk yarn and pile fabric having different pile thicknesses. In thisprocess shrunk fibers are usually worked up in admixture With a certainproportion of shrinkable fibres and the spun yarn or pile fabric iscontacted with hot water at about 100 C. The shrinkable fiber portion isshrunk in this treatment, so the result that the pie-shrunk fibers of ayarn form undulations and curves, a high bulk yarn is produced. Whenpile fabric is subjected to the same hot Water treatment on the otherhand, a finished product having different pile thicknesses is obtained.

The bulkiness of a yarn and the differences in pile thickness of pilefabric can therefore largely be adjusted by the amount of shrinkage theshrinkable fibers used undergo.

It is also known that shrinkable fibers of suflicient strength andelongaton can be produced from certain acrylonitrile copolymers bysubjecting the spinning bands obtained by the dry spinning process torelatively slight stretching, for example to 180 to 250% of the initiallength, and cutting the thread bundle up into staple fibers. The maximumshrinkage which these fibers undergo on boiling is 35 to 38%. By workingup these fibers alone, yarn which has a maximum boiling shrinkage of 38to 41% can be obtained as a result of spinning the yarn right to theend. The shrinkage values obtainable on boiling fibers and yarns in thisway are, however, still insuflicient for some purposes.

A process for the production of high shrinkage threads, yarn and fibersfrom acrylonitrile polymers or copolymers containing at least 50% byweight, and preferably at least 85% by weight, of polymerizedacrylontrile, together with other monomers compatible therewith have nowbeen found which is characterized in that thread or yarn obtained by thedry spinning process is exposed to temperatures of 100 to 180 C. in thepresence of steam and is then stretched at temperatures below 100 C. anddried.

The acrylonitrile polymers and copolymers containing at least 50% byweight, and preferably at least 85% by Patented June 12, 1973 weight, ofpolymerised acrylontrile which can be used in the production of the spunthreads are already known in the art of synthetic thread and fiberproduction. Polymers of this type are obtained by copolymerization ofacrylonitrile with one or more copolymerizable monoolefinicallyunsaturated monomers. Suitable monoolefinically unsaturated monomersare, for example, methacrylonitrile, vinyl chloride, vinylidenechloride, vinyl bromide, styrene, umethylstyrene or the esters ofunsaturated carboxylic acids such as acrylic acid esters and methacrylicacid esters. Vinyl esters such as vinyl acetate, the amides ofmonoolefinically unsaturated carboxylic acids, such as acrylic acidamide and methacrylic acid amide, monoolefinically unsaturatedcarboxylic acids themselves such as acrylic acid and methacrylic acid,and other monoolefinically unsaturated compounds which contain acidic orbasic groups, such as vinyl sulphonic acid, styrene sulphonic acid,inmethacryloylaminodiphenyldisulphimide, methacrylic acidN,N-dimetl1ylhydrazide or vinyl pyridines may also be used. The choiceof comonomers is not critical in the practice of the process accordingto the invention. Any monoolefinically unsaturated compound which can becopolymerized with acrylontrile may be used.

It is unimportant in the production of the threads and yarn by the dryspinning process whether the polymers are produced by the process ofprecipitation polymerization and are then dissolved in a suitableorganic solvent for spinning, or whether polymerization of the monomermixture is carried out in such a solvent itself. Inorganic and/ ororganic pigments such as titanium dioxide or color pigments or solubleadditives may be incorporated in the acrylonitrile threads when spinningthem without affecting the efficiency of the process of the invention.

When carrying out the discontinuous process according to the invention,the thread or yarn containing at least 15% by weight and preferably morethan 40% by weight of water (based on the dry thread) are introduced ina freely shrinkable state into a chamber heated to to 180 C., preferablyto to C. An atmosphere of steam is produced by evaporation of the water,which atmosphere in conjunction with the ambient temperature causesshrinkage of the spinning material. After termination of the shrinkageprocess, the thread or yarn is cooled and subjected, at a temperaturebelow 100 C., to the after-treatment process which is described ingreater detail below.

The shrinking of the individual threads only takes a few seconds,depending on the selected temperature. In order to carry out theshrinkage step, however, the period of resistance of the spinningmaterial in the shrinkage chamber may vary from a few seconds to severalminutes, depending on the amount of water in the spun material and thetemperature in the chamber. A longer residence period for the shrunkmaterial at elevated temperaturs should, however, be avoided becauseotherwise the color of the unbleached and undyed threads is adverselyaffected.

When carrying out the process discontinuously and in particular whentreating larger quantities of spun material containing little or nowater, saturated steam under an absolute pressure of at least 1.1 kg.wt./cm. and preferably 1.5 to 4.0 kg. wt./cm. may be used in a pressurechamber to adjust the steam atmosphere and temperature. The spun threador yarn is deposited for this purpose free of tension, under conditionsin which it is free to shrink, in perforated metal containers which areinserted in the pressure chamber. The saturated steam is then introducedat the desired pressure into the pressure chamber which may if desiredpreviously have been evacuated. After termination of the shrinking step,the chamber is briefly opened to relieve pressure and may be evacuated,when partial drying and cooling of the shrunk spun material occurs. Theshrinking step may be completed by briefly repeating the saturated steamtreatment in the pressure chamber followed by relief of pressure severaltimes.

When carrying out the process according to the invention continuously,apparatus heated to 100 to 180 C., preferably 110 to 160 C. ispreferably used. The apparatus may contain, as transport elements, drumsieves or rollers having different speeds of rotation or belts, whichensure free shrinkage of the transported spun threads or yarn when theprocess is carried out continuously. The water content of the spunmaterial introduced should again be at least 15% by weight andpreferably more than 40% by weight, based on the weight of thread.Spinning material containing little or no water may, of course, also beworked up in the present invention. In such as case, care should betaken to ensure the steam atmosphere, which is absolutely essentialduring the shrinking step, is maintained by introducing steam into theheated apparatus. There are thus two possible methods of steam treatingmaterial obtained by the dry spinning process within the giventemperature range according to the invention:

(1) Dry heat treatment of wet spun material (2) Hot steam treatment ofdry or only moist spun material.

Shrinking of the spun thread or yarn can also be carried out by acombination of the discontinuous and the continuous mode of operation.

When producing the high shrinkage thread, yarn and fiber, the spunmaterial which has been shrunk as described above is then stretched to180 to 320% of its initial length in a water bath at temperatures below100 C., preferably at 65 to 95 C., after having been dressed with anantistatic preparation, and is dried in a heated apparatus. The dryingtemperature should be of the same order as the stretching temperature inall the operations following the stretching process. In order to producefibers, the yarn is crimped and cut up to the desired staple length.

Thead, yarn and fiber produced in this way have, on average, 10 to 25%higher boiling shrinkage than when the spun material has been treatedunder known conditions and/ or when after treatment is carried out above100 C. Fiber which have a boiling shrinkage of about 50% can thereforebe easily produced.

The boiling shrinkage K is determined by treating an individual threador thin yarn of initial length 1 (in practice measured under apre-tension of 0.01 to 0.02 g./ den.) for 5 minutes without tension withhot water at 98 to 100 C., and then chilling in a water bath of about 20C. The length 1;; is then determined under the same pretension after 30minutes on the shrunk thread or yarn which has been stored free oftension. The boiling shrinkage K is then calculated as a percentageaccording to the equation:

1 1 K%= 111A K EXAMPLE 1 A copolymer of 94% by weight of acrylonitrile,5.5% by weight of methyl acrylate and 0.5% by weight ofmmethacryloylamino diphenyldisulphimide of K-value 84.5 1 is spun by thedry spinning process from a 26.5% by weight dimethylformamide solutionat a draw-off speed of 338/m./min. to form a yarn of 14,000 individualthreads of titre 8.5 den. This yarn which contains 16.4% ofdimethylformamide is placed, free of tension, in 5 kg. portions in aperforated metal container which is then placed in a pressure chamber.The pressure chamber around which hot water circulates is evacuated.Immediately thereafter, saturated steam is introduced into the pressurechamber for 3 minutes, so that the temperatures indicated in Table 1 areachieved. The spun yarn which shrinks in this step is partly dried bythe subsequent evacuation of the pressure chamber, and is cooled belowC.

The steam treated spun yarn is then stretched continuously at 75 C. to220% of its intial length in a water bath which is 5 m. in length, andthe yarn is then washed with Water at 50 C., dressed with an antistaticdressing and dried in a drying drum at 65 to 70 C. To produce thefibers, the stretched yarn is subjected to compression crimping and cutup into fibers mm. in length.

Details of the absolute steam pressure employed, the temperature,shrinkage of the spun yarn, boiling shrinkage of the fibers according tothe invention and their moisture content are shown in Table 1.

The boiling shrinkage of a fiber of a spun material which has not beenshrunk, but which has been aftertreated in the same manner is indicatedunder Example If which is a comparative example.

TABLE I Determined according to Fikentscher, Gellulosechemie 13, 58(1932) Experiment number 1a 1b 1c 1d to It Absolute pressure of thesteam in the pressure chamber (kg.

wt./em. 1.5 1.9 2.3 2.5 8.0 Temperature in the pressure chamber C.) 110118 124 129 133 Shrinkage of the spun yarn in the pressure chamber(percent) 10.7 12.7 13.8 14.0 14.2 Boiling shrinkage of the fiber(percent) 48.0 48.3 50.5 51.0 52.0 35.0 Moisture content of the shrunkfiber (percent) 8.4 7.7 8.3 8.1 7.4 8.6

1 Comparison.

EMMPLE 2 The spun yarn described in Example 1, comprising 1400individual threads of titre 8.5 den., is passed continuously through awater bath at a temperature of 50 C. and is squeezed off between a pairof rollers so that the water content, based on the polymer, is 60 to65%. The spun yarn is then conveyed free of tension on an endless bandthrough a heating cupboard at 135 to C. The spun yarn shrinks by 10% inthe process.

The shrunk yarn is then stretched to 220% of its initial length in waterat 75 C., and is then washed with water at 50 C., dressed with anantistatic dressing and dried at 65 to 70 C. The endless yarn is crimpedin a compression crimpage chamber at 50 C. and cut up into fibers ofstaple length 120 mm.

In a comparative test, a spun yarn which has not been shrunk inafter-treated in the same manner.

In order to test the suitability of the fibers for use in high bulkyarn, a yarn of Nm. 24/1 and T/m. 3202 is completely spun and theshrinkage of the yarn on boiling is determined. When all the yarn isspun, the shrinkage of the yarn on boiling is always slightly higherthan the shrinkage on boiling of the fiber put into the process.

5 EXAMPLE 3 A 22.5% by weight solution in dimethylformamide of a 100%acrylonitrile polymer (K-value 89) containing 0.5% titanium dioxide(based on the polymer) is spun by the dry spinning porcess, at adraw-off rate of 300 m./min. to form a yarn containing 3600 individualthreads of titre 11.6 den. The yarn is carried continuously through awater bath at 45 C. and is squeezed by means of rollers to a moisturecontent of 50 to 55%, based on the polymer. The yarn is then passedthrough a heating cupboard at 140 to 145 C. under conditions of freeshrinkage for 3 minutes. The yarn shrinks by 12% in this step.

The shrunk yarn is stretched in a water bath at difierent temperaturesand different stretching ratios, is dressed with an antistatic dressing,and is dried at 65 to 70 C. The temperature of the stretching vat, thestretching ratio and the shrinkage of the yarn on boiling are entered inTable III.

In a comparative test, an untreated yarn is heat treated at 85 C. underthe same conditions of stretching and drying.

TABLE III Shrinkage on boiling, percent Conventionally Spun threadshrunk, and after-treated after-treated according spun thread to theinvention (comparison) Stretching temperature..- 75 C. 85 C. 85 C.

EXAMPLE 4 A solution of a copolymer of 63% by weight of acrylonitrile,35% by weight of vinylidene chloride and 2% 0f m-methacryloylaminodiphenyldisulphimide in dimethylformamide (solids content of thesolution 35% by weight) is spun by the drying spinning process at adrawolf rate of 360 m./min. to form a yarn containing 5600 individualthreads of titre 8.5 den. Portions of 5 kg. of this spun yarn whichcontains 14.8% by weight of dimethylformamide are deposited free oftension in a perforated metal container. The spun material in the metalcontainers is twice contacted with saturated steam at a pressure of 2kg. wt./cn:l. absolute for 3 minutes at an interval of 5 minutes, in apressure chamber. The spun yarn which shrinks by 5.7% is dried bysubsequent evacuation of the pressure chamber and is cooled below 100 C.

Samples of the steam treated yarn are continuously stretched to 190 and220%, respectively, of their initial length, at 75 C. in a water bath,and are subsequently washed with Water at 50 C., dressed with anantistatic dressing, and dried at 65 to 70 C.

Stretching, shrinking on boiling of the threads produced according tothe invention, and their moisture content are summarized in Table IV.Results of comparative experiments carried out with conventionallyproduced shrinkage threads are also given.

TABLE IV Spun thread bundle Convention-ally shrunk andafterafter-treated treated according spun thread bunto the invention dle(comparison) Stretching to of the clillgbsolute pressure of the steam inthe pressure chamber=2 Kg. wt./

We claim:

1. A process for the production of high shrinkage fiber fromacrylonitrile polymers, copolymers of acrylonitrile and one or morecopolymerizable monolefinically unsaturated monomers, or mixturesthereof consisting essentially of (1) drying spinning said polymer,copolymer or mixture thereof;

(2) heating the fiber obtained by dry spinning said polymer, copolymeror mixture thereof, to a temperature of 100 C. to 180 C. in the presenceof saturated steam at a pressure of 1.5 to 4.0 kg. wt./cm. with thefiber in a freely shrinkable state; then (3) stretching the fiber 180%to 320% of its initial length at a temperature below 100 C.; and then(4) drying the stretched fiber at a temperature below 2. The process ofclaim 1 wherein said heating step (2) is conducted at a temperature ofC. to C.

3. The process of claim 1 wherein said stretching step (3) is conductedat a temperature of 65 C. to 95 C.

4. The process of claim 1 wherein said stretching step (3) is conductedin water.

5. The process of claim 1 in which a shrinkage of at least 5.7% iseffected in said fiber during the step (2) of steam treatment.

References Cited UNITED STATES PATENTS 2,768,868 10/1956 Hewett et al8130.1 2,920,934 1/1960 Schaefer et a1. 8130.l 3,097,415 6/1963 Davis264206 2,761,754 9/1956 Jones et a1. 264182 2,984,912 5/1961 Robertsonet a1 264182 3,164,650 l/1965 Kocay et a1 264206 3,397,426 8/1968 Fujitaet al. 264210 FOREIGN PATENTS 875,052 8/ 1961 Great Britain 269-1827,898 4/1966 Japan 264206 JAY H. WOO, Primary Examiner U.S. C1. X.R.264210 F, 234

UNITED STATES PATENT owner CERWWCA'EE 0F QWRREQTWN Patent No. 3, 739 054Dated 12 June 1973 SON. In Horst Wieden; Alfred Nogaj'; HerbertMa'rzolph It is certified that error appears in the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

COLUMN LINE ERROR l 5 "Noga" should be Nogaj and "Morzolph" should beMarzolph 4 46 I I "1400" should be 14000 0 4 60 v shrunk in" should beshrunk is 6 21 w "drying" should be dry 6 I 53 v I "2691182" should'be264-182 signed and sealed this 25th day of Dec ember- 1973.

(SEAL) Attest:

EDWARD M. FLETCHERJR; RENE Do 'IEGTMEYER Attesting Officer ActingCommissioner" of Patents FORM po'wso 7 USCOMM-DC 6O376-P69 a U.S.GOVERNMENT PRINTING OFFICE: I959 0-366-334

